Apparatus for heat treating



NOV. 14, 1939. v F, 5, DENNEEN 5 AL 2,180,038

I APPARATUS FOR HEAT TREATING Filed March 29. 1934 INVHVTOK$ KIM 1 wPatented Nov. 14, 1939 UNITED STATES PATENT OFFICE APPARATUS FOR HEATTREATING Francis S, Denneen, Cleveland, William C. Dunn, Shaker Heights,and Courtney N. Mitchell, Berea, Ohio, assignors to The Ohio CrankshaftCompany, Cleveland, Ohio, a corporation of Ohio Application March 29,1934, Serial No. 718,002

2 Claims. (Cl. 266-4) The present invention as an improvement on thephysical structure before appreciable segrepending application SerialNo. 689,904 of Dengation of the elements has occurred. Obviously, neenand Dunn filed September 18, 1933, relates with slower heating methodswhich are not subto a hardened or otherwise heat-treated metal ject tosuch close control, the core will be heated 5 article and particularlyto the means for proto a much greater depth, involving the disposal 5ducing this article. It is directed primarily to of much more heat inthe quench, preventing an article having a surface or zone possessingclose control of the physical structure and detriphysical propertiesdifferent from those of other mentally affecting the physicalcharacteristics of portions of the article. Its field of application thecore.

includes all articles requiring a hard surface such While in theaccompanying drawing and speci- 10 as crankshafts and camshafts forengines, gears fication we have illustrated and described our fortransmission machinery, bearings, and wearinvention as applied tocertain purposes, we do ing surfaces for machine tools, turbines, andcomnot limit ourselves to the construction shown pressors and allpurposes where heavy loads at and described. From the disclosure herein,obvihigh surface velocities are carried or where wear ously, manymodifications and other uses will 15 may occur due to imperfectlubrication, high unit readily suggest themselves to those skilled inthe pressures, or other causes. art. The appended claims define thenovel fea- With our apparatus, it is possible to control tures to whichour invention is limited. the depth, contour and hardness of thehardened In the annexed drawing we show the mechazone, and to insure aproper bond between the nism employed in our invention. 20 hardened zoneand the core. With a definite kind In the drawing is sh w a p 0finductors of steel susceptible to hardening, a definite conand I6hingedly connected at I! and having an tour for the inductor, a definiteair gap, a definite interconnected means for controlling the flow ofcurrent frequency in the electrode, and a definite the coolant. In thepresent case, the inductors I5 5 current density in the electrode, thetemperature and ii are spaced from shaft l8 by means of the and depth towhich the affected zone is heated adjustable stop screw l9 which isprovided with can be closely controlled merely by controlling aninsulating thimble 20. The thimble, bearing the time of application ofthe heating current. Of against the inductor l5 spaces the two inductorscourse, one or more of the other variable factors to define a workreceiving space. An electric than time may be altered for the purpose ofconcurrent, usually of low voltage and high fre- 30 trolling theheating. quency, is supplied by the conductors 2| and 22. With thetemperature and depth of the heated It is desired that the current inpassing through zone closely controlled, it is then only necessary theinductors be confined largely to the inner to properly quench the heatedzone in order to atwalls 23 adjacent to the shaft [8. In order to tainthe desired hardness. Having raised the confine all the current to theseinner walls, the 35 zone to be hardened to the proper temperature, outerwalls 24 may be made of separate pieces of it is vitally important tocool that zone almost insulating material. The current thus passinginstantly, and while it is still within the proper through walls 23induces in the surface of the temperature range, in order to obtain thedesired shaft l8 eddy currents of an intense nature. If 45 hardness, andfurther, in order that the bond the shaft I8 is made of magneticmaterial, conbetween the hardened zone and the core be siderableelectric energy is dissipated in heat in strong and firm and not liableto fracture. By its outer portion by the hysteresis effect. Theemploying the proper current frequency and with combination of thehysteresis and eddy currents proper control and adjustment of the otherfacrapidly heats the surface of the shaft to the 5 tors, the depth ofthe heated zone may be closely point of decalescence. At thistemperature the controlled, and may be kept shallow enough to hysteresiseffect becomes negligible and further make it possible to quench theentire zone fast heating is by the eddy currents. With a given enough toobtain the desired hardness, and to fix shaft I8, the rate of heating ofthe surface of the physical characteristics of the steel, including theshaft depends upon the current density in its structure, within thedesired limits. the walls 23, upon the cyclic frequency, and upon 50 Toinsure a proper bond between the hardened the air gap 25 existingbetween the conducting zone and the core, it is essential that the bondwalls 23 and the surface of the shaft. area contain little or no freeferrite. To attain While it is possible to provide a current source thiscondition it is necessary to almost instantly of variable frequency,this is not regarded as cool the entire zone to be hardened, so as tofix necessary or as a general thing even practicable, 55

hence a fixed frequency found most generally satisfactory for the classof work to be handled is chosen. The current consumption and rate ofheating then are regulated by adjustments in the current supply and bythe regulation of the air gap through the manipulation of screw I!)which is locked in adjusted position by nut 26. The shaft 18 may berotated or oscillated to distribute the heat as desired.

As the results of the heat-treatment of the surface of shaft l8 dependnot only on the rate and intensity of heating, but upon the rate andintensity of quenching, an adequate means for the rapid and properlydirected delivery of a suitable coolant is required. This is provided bymaking inductors l and I6.with a substantial space between the innerwalls 23 and the outer walls 24 to serve as a means of distributtion ofcooling fluid. This fluid is supplied under pressure by the pipe line 21and is delivered automatically to flexible delivery lines 28 and 29 bythe valve 30 whch is operated by lever 3| and the link 32, the latterbeing connected to the in-' ductor IS in such a way as to open the valve30 upon an opening movement of the latter inductor. The quenching mediumfor this purpose may be any fiuid such as water, or a caustic hydroxidesolution which we have found to possess unusual cooling qualities. Thisquenching medium supplied through the lines 28 and 29 enters theinductors I5 and Hi from where it is delivered in the required volume bythe oriflces 33 in the inner walls 23 of the inductors. The orifices 33are so arranged as to size and location that a vigorous quenching of theshaft l8 takes place uniformly over the entire heated surface. However,if shaft I8 is not uniform in shape, or is unequally heated, the rate ofquenching at various points on its surface may be regulated by the sizeand spacing of the orifices.

In order to interrupt the heating provided by current from conductors 2iand 22, which are usually connected to secondary coils of a.transformer, the current in the primary circuit of this transformer isinterrupted substantially simultaneously with the application of thequenching fluid or just before or immediately after this application.This is accomplished automatically by the switch 34 which controls theflow of cur-' rent in the conductors 35 and 36 of the primary circuit.This switch is opened by the initial movement of inductor l5 through themedium of screw 31 adjustably secured in this inductor and locked in itsadjusted position by nut 38, a suitable insulator such as 39, beingprovided between the screw and the current carrying ele ments of theswitch.

It will be evident that the apparatus shown and described, ormodifications of it, may be employed for hardening numerous otherarticles such as round or polygonal bars, spherical members, tubing ofvarious forms, strips and rolled shapes. In the treatment of smallarticles such as bolts, studs, piston pins and bushings, the operationmay be made continuous by including suitable conveyors which may movecontinuously in one direction, or which may be intermittent intheirmovements, orwhich mayhave reciprocating movements. The latterarrangement is applicable in the treatment of bolts and the like wherethe body of the piece is to be hardened and another part such as thehead is to remain soft.

It will be evident that all of the articles of a group such as pairs ofpins of a crankshaft, can be hardened simultaneously by providingduplicate and parallel sets of inductors and their related parts. Byproviding other sets of inductors or by moving one set relative to othergroups of surfaces, numerous groups can be hardened consecutively.

It is known that mechanically working metal by such processes asforging, rolling or drawing, changes its physical properties, usuallyimproving them to a marked extent. These improvements are almostinvariably lost in subsequent heat treatments. By the use of the presentprocess, the properties thus acquired are distributed only in thesurface zone heated, thus leaving the material as a whole insubstantially its former condition.

Other modes of applying the principle of our invention may be employedinstead of the ones explained, change being made as regards the meansherein disclosed, provided those stated by any of the following claimsor their equivalents be employed.

We, therefore, particularly point out and distinctly claim as ourinvention:

1. In apparatus of the character described, the combination of aconductor adapted to be brought into operating relationship with anarticle to be hardened said conductor being in two parts connected by ahinge to permit relative movement of the parts, means for establishing aflow of current through said conductor, the conductor having meansassociated therewith for applying quench to the article, the last namedmeans being actuated by a movement of one of said parts of theconductor.

2. In apparatus for heat treating an article, a conductor in spacedrelationship with a surface of the article, means for establishingcurrent in said conductor, a temperature responsive element extendingthru a wall of the conductor, the conductor having a cooling jacketsurrounding a part of the element, means being connected with theelement for controlling the aforesaid current, and means for projectinga cooling fluid onto the surface of the article in cooling proximitywith a part of the element.

FRANCIS S. DENNEEN. WILLIAM C. DUNN. COURTNEY N. MITCHELL.

